Dick Margaret A, Dobbie Kiryn, Cooke David E L, Brasier Clive M
New Zealand Forest Research Institute, Forest Biosecurity and Protection, Rotorua, New Zealand.
Mycol Res. 2006 Apr;110(Pt 4):393-404. doi: 10.1016/j.mycres.2006.01.008.
A locally severe crown disease of exotic plantation Eucalyptus trees has been recorded periodically in New Zealand since 1986. Symptoms include leaf spots, petiole infection and twig and small branch lesions. Outbreaks of disease are episodic and individual trees may show marked variation in crown symptoms ranging from unaffected to total defoliation. Two previously unknown species of Phytophthora are associated with the disease. These are described and formally designated here as P. captiosa, from Eucalyptus botryoides and E. saligna; and P. fallax, from E. delegatensis, E. fastigata, E. nitens and E. regnans. Both P. captiosa and P. fallax have non-papillate, non-caducous sporangia and both are self-fertile. Phylogenetic analysis on the basis of ITS rDNA sequence data indicates they are closely related to each other but evolutionarily distant from the majority of described Phytophthora taxa. They share a common ancestor with another assemblage of Phytophthora lineages that includes P. insolita, P. macrochlamydospora and P. richardiae. Sporulation of P. captiosa and P. fallax has not been observed in the field. The mode of infection and spread of these non-caducous Phytophthora species in the eucalypt tree canopy remains unknown. This issue, and the possible geographic origins of these two Phytophthora species are discussed.
自1986年以来，新西兰定期记录到外来人工林桉树出现一种局部严重的树冠病。症状包括叶斑、叶柄感染以及嫩枝和小枝病变。病害爆发具有间歇性，单株树木的树冠症状可能有显著差异，从未受影响到完全落叶。两种此前未知的疫霉属物种与该病有关。这里对它们进行了描述并正式命名，从瓶桉和柳桉中分离出的为捕获疫霉；从德利桉、直干桉、尼氏桉和王桉中分离出的为隐匿疫霉。捕获疫霉和隐匿疫霉都具有无乳突、不脱落的孢子囊，且都是自育的。基于ITS rDNA序列数据的系统发育分析表明，它们彼此密切相关，但在进化上与大多数已描述的疫霉分类群距离较远。它们与包括奇异疫霉、大孢疫霉和里氏疫霉在内的另一组疫霉谱系有共同的祖先。在野外尚未观察到捕获疫霉和隐匿疫霉的孢子形成。这些不脱落的疫霉物种在桉树林冠层中的感染和传播方式仍然未知。本文讨论了这个问题以及这两种疫霉物种可能的地理起源。
